The field of the present invention is that of a method of cold forming a capped cylinder having a cylindrical surface with geometrically spaced torsional engagement radial projections and the product made thereof. The field of the present invention also covers an apparatus utilized in the method above described.
It is generally known in the art that a metal workpiece which is cold formed typically exhibits better strength characteristics than a metal workpiece which is hot formed. Accordingly, it has been known in the art to have a capped cylinder which is cold formed to provide a torsional force engaging member in an automotive vehicle transmission. When such a cold formed capped cylinder is to have gear teeth or splines along its outer cylindrical surface, typically, the capped cylinder is first cold formed and then the radially projecting splines or gear teeth are formed by removing metal upon an outer cylindrical surface of the capped cylinder by broaching. Although capped cylinders having splines or gear teeth which are first stamped and then broached or machined have performed in an acceptable manner, it is desirable to form such capped cylinders without having to go through the expense of the broaching operation. It is also desirable to form such a capped cylinder wherein the torsional engaging radial projections will have a greater strength than radial projections which have been formed by broaching. It is still another desire to have torsional force transferring radial projections which can meet exacting dimensional requirements without requiring machining.
To make manifest the above delineated desires, the revelation of the present invention is brought forth. The present invention brings forth a method of cold forming a capped cylinder having torsionally engaging radial projections along its cylindrical outer surface. The present invention includes piercing and drawing a circular blank into a capped portion and a cylindrical side portion. In the preferred embodiment of the present invention, the workpiece starts out as a flat disk of steel or other suitable material. The flat blank of steel is center pierced and drawn into a upper capped portion and a lower cylindrical portion. The drawn part is then restruck to further define the top into a generally flat capped portion. The top capped portion is connected to the lower cylindrical wall portion by an intermediate skirt portion. The top capped portion is then center pierced. Holes are also pierced for the location of appropriate fasteners. The top capped portion is then ironed to define a thickness of the capped portion. The workpiece is then placed over a spinning mandrel and placed within a die which has an inner surface with spline teeth. The spinning mandrel is axially brought up toward the die and then cold forms the spline upon the outer cylindrical surface of the workpiece by forcing the cylindrical side portion of the workpiece radially outwards toward the die. In a preferred embodiment, the spinning mandrel also forms an inner rim on the workpiece.
It is an object of the present invention to provide a method of cold forming a capped cylinder having geometrically spaced torsional engaging radial projections on a cylindrical outer surface.
It is an object of the present invention to provide a capped cylinder having a cylindrical portion with torsionally engaging radial projections.
It is a further object of the present invention to provide a spin forming machine which can, on a capped cylinder with a lower cylindrical portion, cold form torsionally engaging radial projections along an outer surface of the capped cylinder in combination with a die.